This invention relates to the generation of electrical energy by piezoelectric elements, and particularly to the generation of electricity by weighted, spring-like piezoelectric elements having particular utility, among other uses, for generating electricity for use in navigation buoys.
Navigation buoys and the like are frequently provided with lights and/or horns for signaling the presence of the buoys to passing vessels. The buoys are preferably unattended for extended periods of time and relatively large and expensive battery systems are disposed within the buoys for providing electrical energy. In recent years, attempts have been made to provide automatic recharging of the batteries by photovoltaic energy generators which convert sunlight to electrical energy. Such systems tend to be expensive and, particularly in salt water environments, the sun absorbing surfaces tend to become quickly coated with light blocking salts and the like.
A need exists, therefore, for means for charging the batteries on a continuous basis for greatly extending the periods between maintenance visits, and preferably by a charging means which can be isolated from surrounding hostile conditions. Such need is satisfied by the present invention which utilizes piezoelectric elements within the buoy.
The use of piezoelectric elements within buoys and floats of various kinds for generating electrical energy is known. In general, the prior known systems include massive elements mounted for reciprocating movements in response to wave induced rocking motions of the floats. By various means, the kinetic energy gained by the massive elements is transferred to piezoelectric elements for the generation of electrical energy. The various energy absorbing and converting systems heretofore used are quite inefficient and thus relatively impractical. The present invention provides a far more efficient and practical system. In copending U.S. patent application entitled, "Piezoelectric Generation of Electrical Power From Surface Waves in Bodies of Water Using Suspended Weighted Members", filed by M. Y. Epstein, there is disclosed, among other things, the use of a float from which is suspended a weighted piezoelectric element. The system functions as a weighted spring which oscillates, preferably in resonance, in response to vertical movements of the float in response to passing surface waves. The present invention is based upon the invention disclosed in such co-pending application, the subject matter of which is incorporated herein by reference.